The present invention relates to scale weight combination selections systems for selecting the most appropriate combination of weights in combinational weight machines.
These combinational weight machines are designed to select from a plurality of product weighing scales, the quantity of product that is most desirable, depending upon the objectives of the system. The product is not limited to foodstuffs and can include hardware product and soft goods products, as well, basically most non-liquid particulate product. These machines generally include an in-feeding system where the particulate product flows in a single stream. In one conventional combinational weighing machine, the bulk material is delivered to a central location in a machine and then fed radially outwardly to each of the scale areas, which generally includes a vibrator and a hopper or chamber to collect product flowing off the vibrator or belt conveyor. These scale chambers may be loaded simultaneously but not necessarily depending upon the speed of the machine.
In the past, scale weight combination selection systems have become increasingly common through the discovery and development of the microprocessor, which is capable of sampling multiple combination scales in a very short period and calculating which combination thus satisfies and provides a target weight. When the best weight combination has been identified, those scales belonging to the combination are dumped into a common chute which discharges the collected product into a package associated with a packaging machine. This process is easily effected repeatedly by a microprocessor with the scales reloaded while the dump scale is eliminated from the search process until they are reloaded.
Examples of these systems which attempt to provide a total weight closely approximating or equaling a target weight include systems disclosed in the Minamida, et al., U.S. Pat. No. 4,396,078, and the Mosher, et al., U.S. Pat. No. 4,466,500.
The versatility and speed of microprocessors permit a multitude of scales to be examined during the search process and permit weight parameters to be easily adjusted in accordance with differing product weight and production demands. It is important that the weight information and scale be accurate throughout extended periods of use and not be effected by drift in the components which process the weight information.
Calibration systems are generally employed in the scale to periodically update the weighing parameters used by the microprocessor. A procedure to weigh an empty scale will determine a tare or correction routinely while machine is in operation.
Furthermore, weight sampling is complicated by environmental factors such as temperature and humidity, as well as the resilient mouths for the vibrator and loading devices, as well as the mounting arrangements for measuring sensors in the scales. All of these elements introduce errors into the weighing process.
There is significant prior art directed to microprocessors for these combinational scale systems, but to a large extent, these systems have been predominantly directed to minimizing the number of calculations to improve cycle speed.
However, with the very marked improvement in event speed for microprocessors of the present day, and the outlook for significant increase in microprocessor speeds in the very near future, the elimination of certain combinational calculations by the microprocessor in prior art systems has practically no effect on present day overall cycle speeds, bearing in mind both the limited number of scales even in higher order machines over 16 scales, and the mechanical limitations of the multiple scale weighing machine itself.
In the Minamida, et al., U.S. Pat. No. 4,396,078, a weighing or counting method is disclosed which provides for the discharge of articles from a weighing machine corresponding to a selected combination, and during the subsequent feeding of fresh articles into the same weighing machines, the system functions at that time to select combinations on the basis of weight data from a fixed number of weighing machines which were not selected or did not discharge from the previous cycle. While such a feature is cycle improving, it in effect doubles the number of scales required because only effectively half the scales are used in every cycle. For example, in higher order scale machines, a 16 effective scale machine would require 32 scales, an extremely large and expensive machine.
In the Mosher, et al., U.S. Pat. No. 4,466,500, a combinational weight system is provided which selects the minimum qualified weight identified through a search operation based upon an ordered search sequence of all combinations of scales. The search is conducted by a search control means which has a means for eliminating from the search, combinations of scales having sub-combinations previously searched and found to be at or above the target weight. Elimination of certain combinations from the search sequence reduces cycle time. The search sequence is also established by adding one new or different scale to the combinations or sub-combinations previously searched. In that manner, the Mosher, et al. system minimizes the volume of data manipulated during each step of the search sequence with an improvement in cycle time. However, because microprocessor cycle times at the time of the 1982 filing date of the Mosher, et al. underlying application, were but a fraction of the microprocessor cycle times today, this system no longer has any significant viable cost-saving benefit.
It is a primary object of the present invention to ameliorate the problems noted above in prior art combination selection systems.
In accordance with the present invention, a scale weight combination selection system is provided for selecting the most appropriate combination scale weights in combinational weight machines.
Combinational weight machines are designed to select from a plurality of product weighing scales, the quantity of product that is most desirable, depending upon the objective of the system. Product is not limited to foodstuffs and can include hardware product, soft goods product, and basically most non-liquid particulate products.
The present system is best utilized in higher order scale weighing machines; namely, 16 scales and above, although the invention is not limited thereto, and includes a microprocessor control that date stamps each of the scale weights as the scales are loaded. The scale weights are then sorted into date stamps and then divided into two groups; the first group being the earlier date stamps, and the second being the later date stamps.
The system then calculates all possible combinations in each group utilizing a digital code with code position representing a specific scale.
Any suitable digital code can be used for this purpose, although a gray code is exemplified in the present detailed description.
Thereafter, the digitally coded marked combinations in each group are sorted, utilizing a unique formula that gives preference to both the earliest date stamp scale weights and the combinations having the greatest number of scales.
An arithmetic logic unit in the microprocessor then sequentially scans the combinations in the first group(primary group) and combines them(adds) in the ranked order with the combinations in the second group(secondary group), also in ranked order. This preferential scanning order is further enhanced by an exact weight comparative system that automatically ends the scanning cycle if an exact weight is achieved. In the absence of an exact weight, however, the ranked order scanning and combining of the primary group combinations with the secondary group combinations will proceed until completion, with one caveat, and that is a fail-safe system ends the cycle in the event that a scale is in the system an excessive length of time, and this sub-system combines that scale and executes a discharge prior to completion of all possible primary group and secondary group combinations.
In order to improve cycle speed, a previous selection of an appropriate combination after discharge is eliminated from the next combination calculation. For example, in a 16 scale machine, if the selected combination is 5, and the appropriate discharge of those 5 chambers was in process, the system can begin a new cycle combination on the remaining 11 scale chambers instead of delaying the process awaiting the loading of the 5 used chambers. In that instance, all of the feeding devices, whether they be belts or vibrators associated with the scale chambers, would not be operating simultaneously. These feeders, one being provided for each scale, can deliver product either into a chamber upstream of the scale, or in some cases in less expensive systems, directly to the scale itself. These feeding devices are timed so that they feed an approximate fractional target weight of product into the scale upstream chamber. These upstream chambers are then discharged onto the scales where they are weighed and the weights of each scale are then stored in memory.
These weights are stored in a microprocessor which usually computes all possible scale weight combinations but in higher order scales(above 16) limits the number of combinations to reduce cycle time. In order to understand how the present systems work, it is necessary to provide a definition of xe2x80x9ctarget weightxe2x80x9d. In a 16 scale system, the target weight may, for example, be 1 lb. or 16 oz. In a 16 scale machine in which the total target product weight is 16.0 oz., the fractional target weight for each scale should be selected at 2 oz. because 2 oz. requires the use of 8 scales. Eight scales in a 16 scale machine have 12,870 combinations, while 7 scales have 11,440, as does 9 scales. Therefore, the 8 scale combination has the greatest number of combinations, and hence, the greater likelihood for achieving delivery closer to the target weight of 16.000 oz.
In one case, these scales are positioned within a funnel-shaped device, or a common reservoir that fills the product package at the total exact target weight. Each scale has a solenoid operator that, in most cases, pivots a door or a flap to discharge the product into the funnel. Stepper motors can also be utilized instead of solenoids. Typically, there is a single funnel in a circular type machine that surrounds all of the scale areas and provides the common discharge into the single product package.
There are also inline machines which utilize a single rectangular hopper.
In accordance with the present invention, the microprocessor arranges each of the stored scale weights according to time in the system and gives the highest priority to that scale that has been in the system the longest. For example, if scale number 12 were in the system the shortest time, it would be ranked first after rearrangement by the microprocessor, and all combinations using scale 12 are computed first. In this process, each of the scales is given a time stamp so that the oldest in the system scale will have the earliest time date. This rearrangement of scale weights into time priority occurs on each cycle of the machine. In the above example, when 8 of the 16 scales have been discharged, half of those 8 scales have been refilled, and they each will receive a new time stamp and, of course, they will have approximately the same time stamp. The refilled machines will then have a later time stamp and less priority and thus the unused scales in the next combination cycle will be the preferred scales, but not necessarily the ones selected depending upon the weight calculation which will be explained hereinafter.
While this rearrangement process occurs each cycle, it does not necessarily occur at a particular point in the cycle and is not critical thereto.
As discussed above, this rearranged scale order is then divided in half into two groups: one, a primary group;
and one, a secondary group. The primary group consists of the first 8 scales with the earliest time stamps, and the secondary group consists of the remaining 8 scales with the later time stamps. The methodology in dividing the scale weights into primary and secondary groups is to facilitate combining each primary group weight with each secondary group weight to analyze the weight combinations.
Thereafter, using a gray code or some other digital combination code, the microprocessor calculates all possible weight combinations in the primary group and all possible weight combinations in the secondary group, and those are stored in memory.
Then the microprocessor uses a ranking order for the primary and secondary group combinations utilized to combine each combination in the primary group with all of the combinations in the secondary group. In this machination, the combining calculation begins with by combining all of the scales in the primary group with each of the scales in the secondary group in the ranking sequence. The combination of all 8 primary scales then proceeds next with a combination of 7, 6, 5, 4, etc. of the scales in the secondary group, then 8, 6, 5, 4, etc.
This same calculation continues next with 7 of the oldest scales in the primary group combined first with 8 of the scales in the secondary group and then [sequentially] the next ranked combinations 7, 6, 5, 4, etc., then 8, 6, 5, 4, etc. and repeated in order of the ranking formula.